U.S. patent number 4,667,737 [Application Number 06/861,553] was granted by the patent office on 1987-05-26 for sealing apparatus.
This patent grant is currently assigned to Baker Oil Tools, Inc.. Invention is credited to James G. Shaw, John H. Shore.
United States Patent |
4,667,737 |
Shaw , et al. |
May 26, 1987 |
Sealing apparatus
Abstract
A sealing apparatus having particular utility in a submersible
electric motor utilized in subterranean wells comprises a tubular
housing assembly securable in upwardly projecting, sealed
relationship to the motor housing. An extension of the motor shaft
projects upwardly through the tubular housing to drive a pump or
other subterranean well tool. The upper end of the extension shaft
is exposed to well fluids and a first shaft seal is mounted in a
seal mounting chamber defined in the upper end of the tubular
housing assemblage. Below the seal mounting chamber, the tubular
housing assemblage defines a diaphragm chamber. A conduit is
provided between the lower portions of the seal mounting chamber
and the lower portions of the diaphragm chamber. A flexible,
annular diaphragm divides the diaphragm chamber and is exposed on
its exterior to well fluids, and on its interior to a light density
motor protective fluid, thus equalizing any pressure differential
between the motor protective fluid and the external well fluids.
The diaphragm chamber is connected at its upper end to a downwardly
extending axial passage surrounding the motor shaft and
communicating with the interior of the motor housing.
Inventors: |
Shaw; James G. (Oklahoma City,
OK), Shore; John H. (Shawnee, OK) |
Assignee: |
Baker Oil Tools, Inc. (Orange,
CA)
|
Family
ID: |
25336124 |
Appl.
No.: |
06/861,553 |
Filed: |
May 9, 1986 |
Current U.S.
Class: |
166/104; 277/336;
277/409 |
Current CPC
Class: |
F16J
15/004 (20130101); E21B 4/003 (20130101) |
Current International
Class: |
E21B
4/00 (20060101); F16J 15/00 (20060101); E21B
041/00 (); F16J 015/40 (); F16J 015/54 () |
Field of
Search: |
;166/104,105,68,242
;277/135 ;175/104,107 ;417/424,366 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Attorney, Agent or Firm: Norvell & Associates
Claims
What is claimed and desired to be secured by Letters Patent is:
1. Sealing apparatus for a downhole well motor having a shaft
extension projecting upwardly out of the motor housing containing
the motor windings, comprising, in combination:
a tubular housing surrounding the motor shaft extension and having
a lower portion sealingly securable to said motor housing;
said tubular housing assembly defining an annular seal mounting
chamber in its upper end;
a shaft seal disposed in said seal mounting chamber to prevent well
fluid leaking down said shaft into said chamber;
said tubular housing assembly further defining an annular diaphragm
chamber below said shaft seal mounting chamber;
a flexible annular diaphragm sealingly mounted adjacent the outer
periphery of said annular diaphragm chamber, thereby defining a
fluid expansion chamber within said flexible diaphragm,
axially extending first conduit means connecting the lower portions
of said seal mounting chamber with the lower portions of said fluid
expansion chamber;
means for filling said seal mounting chamber and said expansion
chamber with a motor protective fluid having a lighter density than
well fluids; and
second conduit means in said tubular housing assembly defining a
fluid path for well fluids to surround the outer surface of said
flexible annular diaphragm; whereby pressure differentials between
well fluids and said motor protective fluid are equalized.
2. The apparatus of claim 1 further comprising means in said
tubular housing assembly defining an annular, downwardly extending
passage adjacent said shaft to transmit said motor protective fluid
to the motor windings; and port means interconnecting said annular
passage with said expansion chamber at a level substantially above
the lower end of said second conduit means, thereby creating a
labyrinth flow barrier for well fluids leaking into said seal
mounting chamber.
3. The apparatus defined in claim 2 further comprising means in
said tubular housing assembly defining an annular labyrinth chamber
below said diaphragm chamber; third conduit means connecting the
upper portions of said downwardly extending annular passage with
the lower portions of said labyrinth chamber; a second shaft seal
preventing downward flow of the protective fluid past said
labyrinth chamber; means in said tubular housing assembly defining
a second downwardly extending annular passage around said shaft
extension communicating with the motor windings; a second port
means connecting the upper portion of said second downwardly
extending annular passage with the upper portions of said labyrinth
chamber, thereby extablishing a second labyrinth fluid barrier for
well fluids leaking into said seal mounting chamber.
4. The apparatus defined in claim 2 wherein said downwardly
extending annular passage is defined by a tube mounted in said
tubular housing assembly in radially spaced, concentric
relationship to said shaft extension.
5. The apparatus defined in claim 3 wherein said first mentioned
downwardly extending annular passage is defined by a tube mounted
in said tubular housing assembly in radially spaced, concentric
relationship to said shaft extension, and said second downwardly
extending annular passage is defined by a second tube mounted in
said tubular housing assembly below said second shaft seal in
radially spaced, concentric relationship to said shaft extension.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sealing apparatus for a submersible
electric motor, and particularly a motor employed to drive a pump
in a subterranean well.
2. History of the Prior Art
Electric motors have long been utilized to pump well fluids from
subterranean wells. Normally, the motor and pump are located at
substantial distances below the surface and are surrounded by well
fluids. Since the well fluids to be pumped must penetrate the
housing of the pump, it is unavoidable that the well fluids will
come into contact with the shaft connecting the electric motor and
the driven pump. Shaft seals in a large variety of configurations
have been employed to prevent the leakage of well fluids downwardly
along the shaft and into the motor housing, thus destroying the
electrical insulation necessarily provided for the motor windings.
Additionally, it is common practice to fill the interior of the
motor housing with a high dielectric protective oil and this same
oil has been provided in surrounding relationship to the shaft
seals and bearings to absorb heat that is necessarily developed in
the normal operation of the motor. When such protective fluid is
employed, care must be taken to equalize the pressure of the
confined protective fluid with that of the well fluids surrounding
the motor for the reason that the existence of a substantial
pressure differential in either direction will greatly contribute
to leakage of the protective fluid of the motor enclosure, or
worse, leakage of the well fluids into the motor housing.
To provide such pressure equalization, the prior art has resorted
to the use of diaphragms which are disposed intermediate the motor
protective fluid and the well fluid to achieve constant
equalization of pressures therebetween through the expansion or
contraction of the flexible diaphragm. Even this precaution does
not preclude eventual leakage of well fluids into the interior of
the motor housing resulting in a substantial reduction in the
useful life of the downhole electric motor.
SUMMARY OF THE INVENTION
The invention provides a sealing apparatus for a downhole electric
motor of the type employed for driving pumps in a subterranean
well. Such sealing apparatus comprises a tubular housing assembly
sealably attachable to the downhole motor housing and extending
upwardly in concentric relationship to an extension shaft connected
to the driving shaft of the motor and utilized to drive a pump. At
the upper end of the tubular housing assembly, a seal mounting
chamber is defined and within such chamber a double acting shaft
seal is disposed to minimize leakage of well fluids downwardly
along the shaft surface. The seal mounting chamber is connected by
downwardly extending passages to the lower portions of an annular
diaphragm chamber which is defined between a tube surrounding the
motor extension shaft in radially spaced relationship and the
inside surface of the outer tubular wall of the tubular housing
assembly. Within this diaphragm chamber, a flexible annular rubber
diaphragm is centrally and sealably mounted. Radial ports are
provided at the upper end of the diaphragm chamber in the inner
tube, thus providing fluid communication between the inner
diaphragm chamber and an annular axial passage extending downwardly
and communicating with the interior of the motor housing.
The seal mounting chamber and the inner diaphragm chamber are
filled with motor protective fluid concurrently with the filling of
the motor housing with such fluid. The external surface of the
flexible diaphragm is exposed to well fluids. Thus, any pressure
differentials existing between the motor protective fluid and the
well fluids are absorbed by contraction or expansion of the
flexible diaphragm.
In the event of leakage of the well fluid past the first of the
double shaft seals, such well fluids, being heavier than the motor
protective fluid, will flow by gravity to the bottom of the inner
diaphragm chamber. They will be trapped in such chamber until the
level of leakage well fluids reaches the ports disposed at the top
of the diaphragm chamber, hence cannot flow downwardly into the
motor housing until such level is reached.
In a preferred embodiment of this invention, the downwardly
extending, annular passage around the extension shaft communicates
with a labyrinth chamber which is defined between a second tube,
which surrounds the shaft extension in radially spaced concentric
relationship, and the inner surface of an outer tubular element of
the housing assemblage. A downwardly extending fluid passage
communicates from the first mentioned downwardly extending annular
passage around the shaft to the bottom portion of the labyrinth
chamber. Fluid can exit from the labyrinth chamber only through
radial port means provided at the top of such passage which
communicate with the top of the second axially extending passage
which communicate through a tube to the bottom of a second
labyrinth chamber. Fluid can exit from the second labyrinth chamber
only through radial port means provided at the top of such chamber
which communicate with the top of another downwardly extending
annular passage surrounding the extension shaft. From there, fluid
communication is provided through the bearings for the shaft
extension and thence downwardly into the interior of the motor
housing. Thus, a substantial amount of well fluids must leak past
the first of the double shaft seals so as to fill both the
diaphragm chamber and the labyrinth chamber before gaining access
to the downwardly extending axial passage leading to the interior
of the motor housing. The time required for this significantly
large quantity of well fluid leakage to make its way past the first
of the double shaft seals and the two labyrinth passages
respectively defined in the diaphragm chamber and the labyrinth
chamber, is substantially increased, thereby increasing the useful
life of the motor by protecting the windings thereof from contact
with well fluids.
Further advantages of the invention will be readily apparent to
those skilled in the art from the following detailed description,
taken in conjunction with the annexed sheets of drawings, on which
is illustrated a preferred embodiment of the invention.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A an 1B collectively represent a schematic vertical
sectional view of a sealing apparatus embodying this invention,
FIG. 1B being a vertical continuation of FIG. 1A.
DESCRIPTION OF PREFERRED EMBODIMENT
A sealing apparatus for a submersible motor embodying this
invention comprises a tubular housing assembly 10 which is sealably
attached to the top end of the housing 1 of any conventional
submersible electric motor, the details of which are not shown. An
end flange 1a on such motor housing mates with a flange 10a
provided on the bottom of the tubular housing assemblage 10, and
bolts 1c clamp such flanges together. An O-ring 1b effects a seal
of the connection. The motor shaft 1d is provided with splines 1e
which engage corresponding splines provided in the lower end of a
coupling 2. The upper end of coupling 2 has an internally splined
sleeve 2a press fitted therein which receives the splined bottom
end 5a of a motor shaft extension 5 which projects upwardly in
concentric relationship to the tubular housing assembly 10 and
terminates in a splined end 5b which is connectable by conventional
apparatus to a subterranean well pump (not shown).
The tubular housing assemblage 10 comprises a plurality of outer
thin-walled tubular elements 11a, 11b, and 11c which are
respectively internally threaded at both ends and threadably
engagable with a bottom connecting housing 20, a lower guide
housing 25, an upper guide housing 30 and a shaft seal housing 40.
The shaft seal housing 40 defines a bore 40a surrounding the upper
portions of the motor extension shaft 5. A sleeve bearing 42 is
snugly mounted in the bore 40a and the upper end of sleeve bearing
42 projects above the bottom of a counter bore 40b to cooperate
with the internal bore 50a of a slinger element 50 which is
sealably mounted on the motor extension shaft 5 by an O-ring 50b.
Radial ports 41 are provided between the counter bore 40b and the
exterior of the tubular housing assembly 10, thus permitting well
fluids to surround the slinger 50 and the upper end of the sleeve
bearing 42. Slinger 50 prevents particulates from settling in the
bearing clearance between shaft extension 5 and sleeve bearing
42.
Upper seal housing 40 further defines a series of downwardly
opening, successively larger counter bores 40c, 40d, 40e and 40f.
The counter bore 40c slidably mounts a seal backup ring 43 which
has an O-ring 43a engaging the counter bore 40c.
The counter bore 40d defines a larger diameter annular chamber
within which is mounted a conventional double shaft seal unit 44.
Shaft seal unit 44 incorporates an upper elastomeric seal ring 44a
which is compressed into sealing engagement with the surface of
extension shaft 5 and the adjacent surface of the backup ring 43 by
a seal compression unit including a compression ring 44b, a spring
guide 44c and a compression spring 44d. Identical elements are
provided at the lower end of the double shaft seal unit 44 and
effect the compression of a second elastomeric seal ring 44a by
spring 44d against a seal support ring 46 which is sealably
supported in an adaptor housing 45 by an O-ring 46a. Adaptor
housing 45 is press fitted to the top of an upper guide tube 47,
the lower end of which is press fitted in a counter bore 30b
provided in the bore 30a of the upper guide housing 30. A second
sleeve bearing 48 surrounds shaft 5 between lower seal support ring
43 and the top end of upper guide tube 47.
It should be recognized that any type of shaft seal may be mounted
in the counter bore 40d and that the specific double seal unit 44
shown in the drawings represents only one of a large number of
conventional structures that can be utilized at this point to
effectively reduce leakage of well fluids downwardly along the
exterior of the extension shaft 5.
The exterior of the upper guide tube 47 cooperates with the
internal bore surface of the uppermost outer tubular housing
section 11c to define an annular chamber 60. The central portions
of chamber 60 are employed as an expansion chamber by clamping the
end portions of a flexible annular diaphragm 61 to the lower
portion 45a of the adaptor housing 45 and an upwardly projecting
cylindrical portion 30d of the upper guide housing 30. Conventional
hose clamps 62 may be employed for this purpose. The flexible
diaphragm 61 is formed from rubber or any other suitable
elastomeric material that is not affected by well fluids.
An axially extending passage 44g is provided in the seal mounting
housing 40 connecting the upper counter bore 40b and hence the well
fluids to the outer portions of the expansion chamber 60.
Additionally, an axial passage 45c is provided in the adaptor
housing 45 which extends from the lower end of the counter bore 40d
in which the shaft seal unit 44 is mounted, to the inner expansion
chamber 63 enclosed by the flexible diaphragm 61. Additionally, an
extension tube 45k is mounted in the lower end of the passage 45c
so that fluid coming through such passage is discharged adjacent
the lower end of the inner expansion chamber 63.
A third axial passage 45d is provided in the guide adaptor 45
connecting the top of the inner expansion chamber 63 with an
axially extending passage 44h which leads upwardly to a venting
port 44k which is normally closed by a threaded plug 44m. As will
be later described, the internal chamber 63 defined by the flexible
diaphragm 61, as well as the seal mounting chamber defined by
counter bore 40d is filled with a high dielectic strength oil which
is of substantially lighter density than well fluids. Accordingly,
any well fluids leaking through the shaft seal unit 44 will be
deposited by passage 45c and extension tube 62 adjacent to the
lower portions of the chamber defined by the flexible diaphragm 61.
It follows that such well fluids cannot flow out of the chamber
until sufficient fluids have collected to reach the elevation of
the radial outlet ports 47a provided in upper guide tube 47
adjacent the upper end of the expansion chamber defined by the
diaphragm 61. Moreover, any differences in pressure between the
well fluids and the motor protective fluid will be equalized by
contraction or expansion of the diaphragm 61, as the case may
be.
The upper guide tube 47 defines a downwardly extending annular
passageway 65 which could, if desired, lead directly into the
interior of the motor housing. In accordance with the preferred
embodiment of this invention, the downwardly extending axial
passage 65 is instead sealed off within the upper guide housing 30.
A sleeve bearing 31 and a shaft seal unit 32 are mounted in a
counter bore 30b provided in the bottom end of the upper guide
housing 30. The shaft seal unit 32 may constitute any conventional
shaft seal unit and here is shown as comprising a backup ring 32a,
an elastomeric sealing element 32b, a seal compressing ring 32c, a
spring guide 32d, a spring 32e and a spring backup ring 32f. A
C-ring 32g secures the backup ring 32f to the shaft extension
5.
In the lower portion of the counter bore 30b of the upper guide
housing 30, a mounting ring 35 and a lower guide tube 37 are
mounted by a press fit. Guide tube 37 cooperates with the inner
wall of the outer housing element 11b to define a labyrinth chamber
66. An axially extending bypass passage 30h is provided in the
upper guide housing 30 which communicates between the lower end of
the downwardly extending annular passage 65 and the labyrinth
chamber 66. An extension tube 67 is mounted in the lower end of the
bypass passage 30h so as to deposit any fluid flowing through such
passage in the lower portions of the labyrinth chamber 66. Fluid
can only exit from labyrinth chamber 66 through a plurality of
radial ports 37a provided in the upper end of the lower guide tube
37. It necessarily follows that leakage well fluids must fill
substantially the entire labyrinth chamber 66 before they would
rise to a level permitting them to flow downwardly through the
annular passage 68 defined between the inner wall of the lower
guide tube 37 and the outer surface of the shaft extension 5. A
vent passage 30k extends upwardly from chamber 66 to a radial port
30m which is normally closed by a plug 30n.
The lower guide tube 37 is supported by being press fitted into a
counter bore 25b provided in the central bore 25a of the lower
guide housing 25. A downwardly opening counter bore 25c provides a
mounting for still another sleeve bearing 26.
The lower guide housing 25 is provided with an axially extending
bypass passage 25d communicating with the annular passage 68 at its
upper end and at its lower end with a thrust bearing chamber 69
defined by the internal surface of the lower tubular element 11a of
the tubular housing assembly 10. Additionally, a venting or filling
passage 25e is provided in the housing 25 communicating with a
radial port 25f which is closed by a threaded plug 25g.
A conventional thrust bearing unit 70 is mounted in the thrust
bearing chamber 69. Since such thrust bearing forms no part of the
present invention, it is shown only schematically. Suffice it to
say that the thrust bearings are provided with fluid passages
permitting the motor protective fluid to completely surround the
thrust bearings to provide not only lubrication but also absorption
of any heat resulting from the operation of the bearings.
The lower portion of the thrust bearing chamber 69 is in direct
communication with a large upwardly opening counter bore 20c
provided in the bore 20a of the connection housing 20. The counter
bore 20c has a fluid guide block 21 press fitted therein and such
guide block provides axially extending fluid passages 21a
communicating between the counter bore 20c and the annular space
defined between bore 20a and the exterior of the connecting sleeve
2. An annular porous metal filter 22 is mounted in overlying
relatinship to the upper end of the passages 21a. Filter 22 is
secured in position by a snap ring 23 which is secured to the upper
end of the guide block 21. Thus, any particulates contained in
fluid moving downwardly toward the motor housing 1 are removed from
the downwardly moving stream by the porous metal filter 22.
The operation of the aforedescribed sealing apparatus should be
apparent to those skilled in the art from the foregoing
description. The motor housing 1 and the interconnected chambers
20c, 69, 66, 63 and 40d of the tubular housing assembly are filled
with the motor protective fluid, generally by forcing such fluid
into the motor housing 1 and causing it to rise upwardly, with the
vent plugs 44m, 33g, 25g and 30n removed to permit the venting of
any trapped air. Obviously, as the level of such fluid rises to the
level of the vent plugs, the vent plugs are reinserted.
To facilitate the release of pressure produced by the heating of
the motor protective fluid after the initial fillup, an axial
passage 30p is provided in upper guide housing 30 having its upper
end communicating with the internal diaphragm chmaber 63. A
downwardly inclined passage 30q connects the lower end of axial
passage 30p to that portion of chamber 60 exposed to well fluids. A
check valve 32 is mounted in the top portions of axial passage 30p
to permit only outward flow of the motor protective fluid to
discharge the expansion of such fluid produced during initial heat
up or by any other pressure build up of the motor protective fluid
which cannot be equalized with well fluid pressure by the diaphragm
61.
Well fluids are in contact with the extension shaft 5 only at the
upper end thereof and can only flow downwardly along such shaft by
leakage through the sleeve bearing 42 and the double seal 44. Any
such fluid leakage moves by gravity through the downwardly
extending passage 45c and extension tube 45k into the bottom
portions of the inner expansion chamber 63. The well fluids cannot
move out of the expansion chamber 63 until such chamber is
substantially full of well fluids, following which the leakage well
fluids can flow down the annular downwardly extending passage 65
into the axially extending passage 30h and through the tube 67 into
the bottom of the labyrinth chamber 66. Again, leakage well fluids
can only escape from labyrinth chamber 66 by filling such chamber
to the level of the radial ports 37a from which they can flow
downwardly to the motor housing 1 through the annular passage 68,
chamber 69 and passages 21a, but may pass through the porous metal
filter 22 before they reach the interior of the motor housing.
It is therefore apparent that a substantial amount of time would be
required for the very significant amount of leakage fluid to be
collected in the sealing apparatus so as to permit it to gain
access to the interior of the motor housing.
At the same time, pressure differentials between the motor
protective fluids and the well fluids are completely neutralized by
the action of the flexible diaphragm 61. All heat generated by the
operation of the various seals and bearings is absorbed by the
motor protective fluid and, as mentioned, any pressure increase due
to such temperature rise is readily absorbed by the flexible
diaphragm 61.
It follows that the useful life of a downhole subterranean well
motor employing a sealing apparatus embodying this invention is
significantly increased due to the substantial isolation of the
motor windings from well fluids over a long period of time, even
though some leakage through the seals of the apparatus may
occur.
Although the invention has been described in terms of specified
embodiments which are set forth in detail, it should be understood
that this is by illustration only and that the invention is not
necessarily limited thereto, since alternative embodiments and
operating techniques will become apparent to those skilled in the
art in view of the disclosure. Accordingly, modifications are
contemplated which can be made without departing from the spirit of
the described invention.
* * * * *